1. Field of the Invention
The present invention relates to a coordinates input apparatus, and more particularly, to an improved coordinates input apparatus having a simplified structure and that can be used without the need for extensive special operating space.
2. Description of Related Art
In recent years, easy-to-operate pointing devices such as the mouse or digitizer, have come to be widely used instead of keyboards as an input means for desktop computers and the like.
For example, a mouse or a digitizer can be used with desktop computers and the like.
However, the laptop and other portable computers that have become popular in recent years are often used outdoors, in vehicles, and so forth, that is, in locations where there is no adequate flat surface on which to rest the computer. As a result, there is often little or no space in which to operate a pointing device such as a mouse or digitizer.
In response to such a requirement, a pointing device that tilts when pressed and the resulting angle of inclination sensed has been proposed as one type of suitable pointing device that is compact and requires very little space in which to operate.
A description of such a conventional compact pointing device will now be given with reference to FIGS. 1, 2, 3 and 4.
FIG. 1 is a diagram showing a front cross-sectional view of a conventional pointing device illustrating a state in which a key-top operating portion of the apparatus is in a substantially vertical state. FIG. 2 is a diagram showing a front cross-sectional view of a conventional pointing device illustrating a state in which the key-top operating portion of the apparatus is in a tilted state. FIG. 3 is a diagram illustrating the relative positions of the magnet and the magnetoelectric transducer of the pointing device shown in FIGS. 1 and 2. FIG. 4 is a diagram showing a side view of the magnet and magnetoelectric transducer of FIG. 3.
According to the conventional art, a pointing device 1 comprises an operating part 2, a pressure part 3 and a coordinates sensor 4.
The operating part 2 comprises a key top 2a, a stick 2b fixedly mounted to one end of the key top 2a and consisting of a shaft 2b-1 extending downward and terminating in a distal end formed into the shape of a hemisphere 2b-2 with the rounded half upward (in the drawing), and a holder 2c which forms a sphere when joined to the hemispherical tip 2b-2 of the stick 2b. A flange 2b-3 extends horizontally from a lower edge of the hemisphere 2b-2, around the entire periphery thereof. The hemispherical tip 2b-2 operating part 2 is contained within a container composed of an upper cover 5a with an aperture in the center thereof and a flat housing 5b, with a lower portion of the hemisphere 2b-2 positioned above the center of the housing 5b and supported by a concavity 5b-2 formed in a projection 5b-1 projecting upward from the center of the housing 5b. At the same time, the upper part of the hemisphere 2b-2 is retained in place by an inwardly and downwardly projecting part formed along the edge 5a-1 of the opening in the upper cover 5a. 
The pressure part 3 comprises a cylindrical slider 3a slidably movable in a vertical direction along side walls 5a-2 of the upper cover 5a and a coil spring 3b positioned between the floor of a concavity 3a-1 formed inside the slider 3a and the upper cover 5a and attached at both ends thereto so as to impel the slider 3a downward at all times. A cylindrical projection 3a-2 that projects toward the hemisphere 2b-2 is provided on the slider 3, such that a lower surface of this projection 3a-2 engages the upper surface of the flange 2b-3.
The coordinates sensor 4 comprises a magnet 4a provided on an interior of the holder 2c and a plurality of magnetoelectric transducers 4b mounted on a printed circuit board 6 bonded to a bottom surface of the frame 5, the magnetoelectric transducers 4b being recessedly mounted with respect to the bottom surface of the holder 2c. It should be noted that there are actually four magnetoelectric transducers 4b-1 through 4b-4 displaced a predetermined distance from the center line of the magnet 4a, as can be seen in FIG. 3.
In the pointing device 1 having the structure described above, pressing and moving the key top 2a slides the slider 3a upward against the spring force of the coil spring 3b and, as shown in FIG. 2, the stick 2b is tilted in a given direction. At this time, the magnet 4a built into the holder 2c is tilted with respect to the magnetoelectric transducer 4b mounted on the printed circuit board 6.
Then, by releasing the key top 2a, the spring force of the compressed coil spring 3b returns the key top 2a to an original position before it was manipulated, thus returning the positional relation between the magnet 4a and the magnetoelectric transducer 4b to an initial state as well.
A description will now be given of the principle upon which the coordinates detector of the pointing device 1 operates.
In a case in which the stick 2b is perpendicular to the printed circuit board 6 as shown in FIG. 1, then as shown by the solid line in FIG. 4 the magnet 4a is separated from the four magnetoelectric transducers 4b (shown as 4b-1 through 4b-4 in FIG. 3) by a certain equal distance. Accordingly the magnetic field imparted to each of the magnetoelectric transducers 4b-1 through 4b-4 is essentially equal and thus, for example, if the direction from which the magnetic field is detected is perpendicular to the printed circuit board 6, then the detected magnetic field direction components B1 through B4 of the magnetic flux density passing through the magnetoelectric transducers 4b-1 through 4b-4 would be substantially equal, and therefore the output voltage of each of the magnetoelectric transducers would also be essentially equal.
By contrast, if the stick 2b is tilted with respect to the printed circuit board 6 as shown in FIG. 2, then the distance separating the magnet 4a from the magnetoelectric element 4b changes as indicated by the dashed line in FIG. 4. In the case of FIG. 4, the magnet 4a simultaneously approaches the magnetoelectric transducer 4b-1 and moves further away from the magnetoelectric transducer 4b-3, so the detected magnetic field direction component B1 increases while the detected magnetic field direction component B3 decreases and the output voltages from the magnetoelectric transducers 4b-1 and 4b-3 change as well, with an angle of inclination θ of the key top 2a deduced from a calculation of the difference in output between the magnetoelectric transducers 4b-1 and 4b-3 and further converted into an X-axis coordinate value for the purpose of moving a cursor on a display (coordinate space). Similarly, by calculating the difference in output voltages between the magnetoelectric transducers 4b-2 and 4b-4 the angle of inclination θ of the key top 2a can be converted into a Y-axis coordinate value. That is, XY coordinate values can be obtained when the stick 2b tilts in a given direction based on the direction and angle of that tilt. These XY coordinates are input into a computer and the direction, extent and speed of movement of the pointer or cursor then displayed on the display.
However, the conventional pointing device as described above has a disadvantage in that the restorative force of a compressed coil spring 3b is employed to return the key top 2a to its original position after it has been tilted in a given direction, with the result that the overall size of the conventional pointing device is increased at least by an amount equivalent to that portion of the coil spring 3b that engages the key top 2a, thus limiting the extent to which the pointing device as a whole, and in particular the key top 2a, can be reduced in size and made more compact.